This study is designed to develop a new method of isolating purified islet tissue for transplantation. Animal pancreas are digested by trypsin to single cell preparations. These are purified by several methods to try to increase the islet cells content in the preparation. Then, pseudo-islets are formed by selective aggregation using rotational tissue culture. This forms pseudo-islets which contain a maximum of all four islet cell types and a minimum of contaminating exocrine cells. These pseudo-islets are being studied for their functional release of islet cell hormones and their transplantability to determine if they can be used as a source of tissue for transplanting the diabetic patient.